103
FXUS02 KWBC 300728
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
327 AM EDT SUN JUL 30 2023
VALID 12Z WED AUG 02 2023 - 12Z SUN AUG 06 2023
...HOT TEMPERATURES AND HIGH HEAT INDICES FROM THE SOUTH-CENTRAL
PLAINS AND MISSISSIPPI VALLEY TO THE SOUTHEAST THIS WEEK...
...HEAVY RAIN/FLASH FLOOD THREAT TO FOCUS ACROSS THE NORTH-CENTRAL
ROCKIES STATES AND VICINITY MIDWEEK...
..OVERVIEW
AN AMPLIFIED AND SLOW MOVING UPPER RIDGE WILL SUPPORT ABOVE NORMAL
TEMPERATURES FROM THE SOUTH-CENTRAL PLAINS THROUGH THE
MID-MISSISSIPPI VALLEY TO THE SOUTHEAST FOR MUCH OF THIS WEEK
ALONG WITH HIGH HEAT INDICES. DEEPENED MONSOONAL MOISTURE LIFTING
ON THE WESTERN PERIPHERY OF THE RIDGE THIS PERIOD WILL FAVOR A
SLOW SHIFT OF A MAIN CONVECTIVE RAINFALL FOCUS FROM THE GREAT
BASIN TO THE NORTH-CENTRAL ROCKIES/HIGH PLAINS. MEANWHILE,
SHORTWAVES IN NORTHWEST FLOW WILL SPARK STRONG TO SEVERE
THUNDERSTORMS MIDWEEK ACROSS THE MIDWEST TO THE
APPALACHIANS/MID-ATLANTIC AND UP TO THE NORTHEAST LATE WEEK. THIS
IS ALSO ALONG AND IN ADVANCE OF A ORGANIZED SURFACE LOW/FRONTAL
SYSTEM THAT SHOULD MODERATE CONDITIONS IN WAKE OF PASSAGE.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES SEEM TO STILL HAVE A DECENT HANDLE ON THE
OVERALL PATTERN WHICH FEATURES VARIOUS SYSTEMS/SHORTWAVES OVER OUR
FINE NATION ROUNDING THE BROAD WESTERN AND NORTHERN PERIPHERY OF A
RE-POSITIONED SOUTHERN U.S. UPPER RIDGE. SOME TIMING/DETAILS
DIFFERENCES REMAIN, MOST NOTABLY WITH THE SHORTWAVE ACROSS AND
INTO THE GREAT LAKES/VICINITY LATER WEEK. THE 18/00 UTC GFS/GEFS
RUNS SEEM SLOWER OUTLIERS COMPARED TO THE REST OF THE MODELS AND
ENSEMBLES THAT OFFERS BETTER CONTINUITY.
ACCORDINGLY, THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED
FROM A BLEND OF THE REASONABLY WELL CLUSTERED 12 UTC
GFS/ECMWF/CANADIAN/UKMET AND GEFS/ECMWF ENSEMBLES, ALONG WITH THE
GENERALLY COMPATIBLE 01 UTC NATIONAL BLEND OF MODELS. APPLIED A
BIT GREATER BLEND WEIGHTING TO THE ECMWF/ECMWF ENSEMBLE MEAN TO
BEST MAINTAIN CONSISTENCY WITH THE PREVIOUS WPC FORECAST. THIS
ALSO WORKS WELL IN GENERAL WITH THE NEWER 00 UTC GUIDANCE CYCLE IN
A PATTERN WITH AVERAGE TO BETTER PREDICTABILITY.
..WEATHER/HAZARDS HIGHLIGHTS
THE GREATEST HEAT ANOMALIES SHOULD SETTLE THIS WEEK ACROSS THE
SOUTH-CENTRAL PLAINS TO THE LOWER MISSISSIPPI VALLEY, WHERE ABOVE
NORMAL TEMPERATURES BY 5 TO 10+ DEGREES ARE LIKELY AS ACTUAL
TEMPERATURES NEAR OR EXCEED 100F. THE SOUTHERN PLAINS TO LOWER
MISSISSIPPI VALLEY AND SOUTHEAST MAY EXPERIENCE HEAT INDICES
SOARING ABOVE 105F, EVEN ABOVE 110-115F IN SOME AREAS. RECORD HOT
HIGHS AND WARM MINIMUM TEMPERATURES ARE WIDELY POSSIBLE IN THESE
REGIONS NEXT WEEK.
AREAS FROM THE GREAT BASIN TO THE NORTH-CENTRAL ROCKIES/HIGH
PLAINS WILL SEE DIURNALLY AND TERRAIN DRIVEN CONVECTION AS FUELED
BY DEEP MONSOONAL MOISTURE AND EMBEDDED SHORTWAVE ENERGIES
ON/AROUND THE PERIPHERY OF THE MAIN UPPER RIDGE. QPF, MOISTURE,
AND INSTABILITY FIELDS SEEM TO SUPPORT SLIGHT RISKS OF EXCESSIVE
RAINFALL CONTINUING INTO WEDNESDAY AND THURSDAY ACROSS PORTIONS OF
CENTRAL WYOMING AND NORTH-CENTRAL COLORADO WHERE FLASH FLOOD
GUIDANCE VALUES ARE LOWER AND BURN SCARS.
MEANWHILE, THE NORTH-CENTRAL U.S. CAN ALSO EXPECT SCATTERED STORMS
AS SHORTWAVES/UPPER TROUGHING WORK INTO THE REGION. A HEAVY
RAIN/FLASH FLOODING THREAT WILL LIKELY BE TIED TO THE POTENTIAL
FOR ORGANIZED CONVECTIVE SYSTEMS IN THE NORTHWESTERLY FLOW.
MARGINAL RISKS HAVE BEEN INCLUDED ON BOTH DAYS 4 AND 5 TO COVER
THIS POTENTIAL FROM THE MIDWEST TO THE APPALACHIANS/MID-ATLANTIC,
WITH EVENTUAL MORE CONCENTRATED SLIGHT RISK AREAS POSSIBLE. THIS
ACTIVITY WILL LIKELY WORK ACROSS THE NORTHEAST LATER WEEK IN A
PATTERN TO MONITOR. ACTIVITY WILL ALSO BE AIDED AS AN ORGANIZED
LOW PRESSURE SYSTEM SUBSEQUENTLY TRACKS EASTWARD ACROSS CANADA, AS
A COLD FRONT TRAILS BACK ACROSS THE LOWER 48 AND STALLS BACK INTO
THE CENTRAL PLAINS.
THIS ALL OCCURS WELL TO THE NORTH OF A LEAD COLD FRONT PUSHED
EARLIER PERIOD UNSEASONABLY FAR SOUTH TO OFFER A MORE DEFINED THAN
NORMAL SUMMERTIME CONVECTIVE FOCUS OVER FLORIDA. THERE COULD BE
SOME LINGERING LOCALIZED HIGH RAIN RATES GIVEN STALLING MOISTURE
POOLING/INSTABILITY FOCUS AS THE FRONT SLOWLY WEAKENS OVER TIME.
SCHICHTEL
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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